1. Field of the Invention
The present invention relates in general to the field of information handling system electromagnetic interference, and more particularly to a system and method for managing average emission of electromagnetic interference from an operating information handling system.
2. Description of the Related Art
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Information handling system manufacturers generally attempt to configure information handling systems to have as much processing power as is economically available for a chassis of a given volume. Many of the processing components included in a chassis produce radio frequency (RF) signals as a by product of their operation. The cumulative effect of these RF signals often creates electromagnetic interference (EMI) across a wide spectrum of frequencies. EMI is typically measured by the average amount of RF emissions from a chassis during operation of the processing components and is regulated by government bodies, such as the FCC in the United States and the CISPR in Europe. Typically, as information handling system volume decreases, manufacturers have to use greater care in the distribution of processing components within the chassis so that operational EMI constraints are met. One way to reduce average EMI emissions is to shield the processing components with a chassis that reflects RF energy. Shielding effectively reduces EMI, however, EMI still escapes through the shielding and from unshielded portions of the chassis. Further, excessive reliance on shielding increases the cost, size and weight of an information handling system. Excessive weight and size of an information handling system chassis is typically viewed as a detriment by end users.
Information handling system components have steadily increased their processing capability over the past several years, often by operating at higher clock speeds. For instance, higher-speed serialized interconnects have become more prevalent in information handling systems that emit RF signals of greater than 1 GHz. The concentration of such RF signals at specific frequencies is increased for some serialized interconnects that do not allow for spread-spectrum clocking, such as the Serial-Attached-SCSI (SAS) and Fiber-Channel interconnects. Regulatory agencies have responded by placing restrictions on EMI in higher frequencies that are difficult for information handling system manufacturers to achieve. Often, measured emissions are not sufficiently reduced by existing EMI shielding technologies.